FORW~tD BY.*CHI tt L j I' fRAOTechnical Report
Higher-Strength Steel Weldmants forSubmarine Hulls- Second Status Report
S... .. - - .) .. . -• ..
Applied Research LaboratoryUnited States SteelMonroeville, Pennsylvania
January 4, 1965 Project No. 40.018-001(39)
S!b-Ak540 SR007-01-01 Task 853 S-00000-1RL I ,' IO@•s U.N
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HIGHER-STRL.-rTH STEEL WELDMENTSFOR SUBMARINE HULLS-SECOND STATUS REPORT
(40.018-001) (39) (a-ORD-NP-3) (S-00000-1)
January 4, 1965By J. H. GrossApproved by W. T. Lankford, Jr., Assistant Director
AbstractSince June 1, 1963, U. S. Steel has been engaged in the development
of an HY-130/150 weldment and in a study of the feasibility of developing anHY-180/210 weldment under Bureau of Ships sponsorship. The progress of theprograms was broadly reviewed on April 1, 1964, and is again reviewed in thepresent report.
The accomplishments to date in the HY-130/150 program indicate thata 5Ni-Cr-Mo-V steel has been developed that meets essentially all the re-quirements for an HY-140 steel. When the 5Ni-Cr-Mo-V steel was joined witha 140 ksi yield-strength 2Mn-2Ni MIG filler metal, the resulting weldmentsexhibited good performance in explosion tests. These tests also showed thatwhen the yield strength of the weld metal matched or overmatched that of thebase metal, the deformation characteristics of the weldments were satisfac-tory, whereas those of an undermatching weld metal were unsatisfactory.
Currently, 138 ksi is the typical yield strength for a reliableHY-130/150 type weld metal. Because this yield strength would match that ofan HY-130 production plate (average yield strength of 138 ksi, range of 130to 145 ksi), whereas it would undermatch that of an HY-140 plate, the interimobjective for the HY-130/150 program should be the development of an HY-130weldment for low-hull-fraction high-toughness combatant submarine hulls.Selection of an HY-130 weldment as an intrri objective would facilitateinitiation of the Weldment Evaluation Program (during January 1965) and ofthe Prototype Evaluation Program (during the latter part of 1965), and itwould also facilitate an increase in the typical thickness of an HY-130/150weldment if required. Nevertheless, the development of an HY-140 weldmentwill be pursued on a priority basis with the aim of replacing the HY-130weldment at the earliest possible time.
Results of the HY-180/210 program indicate that the development ofa 180 ksi minimum-yield-strength weldment having a Charpy V-notch energyabsorption of about 50 ft-lb is feasible. However, a significant programincluding the development of improved steel compositions, low-residual melt-ing practices, and special processing techniques for the base metal and fillermetal wil be required. Achievement of this toughness objective may notinsure a wcldment that will be "fracture tough" for large flaws and highstress concentrations. Therefore, the minimum acceptable ": racturetouhness' should be established from studies of improved design, fabrica-ticn, and inspection practices.
UNITED STATES STEEL VU1.1wtWu V L=
Introduction
On June 1, 1963, Bureau of Ships Contract No. NObs-88540 was
initiated to develop a submarine-hull weldment with a yield strength in tie
range 130 to 150 ksi (SR007-01-01 Task 853) and to determine the feasibility
of developing a submarine-hull weldment with a yield strength in th2 range
180 to 210 ksi (SS050-000 Task 1567). The starting points for the plograms
were broadly summarized in a preliminary status report. )*Awer brady smmrizd i apreimnar sttu reor. After 10 months
work, the status of the programs was again reviewed in an interim status
2)report. As of December 1, 1964, eighteen months of the contract period
have elapsed. Therefore, it appears appropriate to again review critically
the accomplishments in terms of the program objectives and to project the
final outcome of the program and the timetable therefor.
The objectives of the HY-130/150 program were established by pro-
jecting the performance requirements for an HY-80 weldment to those for an
HY-130/150 weldment. By so doing, the requirements for a low-hcll-fraction
combatant HY-]30/150 submarine hull would presumably be met. Thus, the
accomplishments to date are being assessed in that context For that reason,
the conclusions and recommendatiors presented herein should not be applied
to the less stringent requirements for a high-hull-fraction submarine or to
the much less stringent requirements for noncombatant submersibles.
Similarly, the feasibility of developing an HY-180/210 weldment is based on
the low-hull-f:action combatant submarine concept.
*See References. -2-
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HY-130/150 Program
In accordance with the Contract outline, the following areas have
been concurrently investigated.
Base-Metal Development
Laboratory evaluaticn of over 300 experimental compositions has
led to the selection of a 5Ni-Cr-Mo-V steel of the composition shown in
Table IA. Table IB shows that when this steel is properly quenched and
tempered, the yield strength ranges from an average of 150 ksi for 1/2-inch-
thick plate to 137 ksi for 4-inch-thick plate. When the steel is melted to
the high side of the composition range, a minimum yield strength of 140 ksi
is attainable in plat..es through 5 inches thick.
At 0 F, full shear fractures are obtained and the Charpy V-notch
energy absorption ranges from 74 ft-lb for 4-inch-thick plate to 101 ft-lb
for 1/2-inch-thick plate. For 1-inch-thick plate, the drop-weight tear
energy absorption is 5000 to 6000 ft-lb, and the thickness can be reduced
more than 40 percent by explosive deformation without fracture. Because the
typical NDT is about -120 F. failure by brittle fracture will not be encoun-
tered at ice-watez temperatures.
In the range 10,000 to 100,000 cycles, the strain to initicate
fatigue cracks in the 5Ni-Cr-Mo-V steel is about the same fraction of its
yield strain as that for HY-80 steel, Figure 1. When the 5Ni-Cr-Mo-V steel
is welded by the inert-gas-shielded metal-arc (MIG) process using an
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experimental HY-130/150 filler metal, the reduction in fatigue strength is
of about the same magnitude as that for HY-80 steel when welded with an
ElI018 covered electrode. Thus, in the cycle life of primary interest, the
fatigue design factors being used for HY-80 steel appear equally applicable
to the 5Ni-Cr--Mo-V steel.
In sea-water corrosion tests, the 5Ni-Cr-Mo-V steel was slightly
more resistant to general corrosion than HY-80 steel. In addition, the
corrosion potential between the 5Ni-Cr-Mo-V steel and the experimental
HY-130/150 MIG weld metal was less than that between HY-80 steel and the
E11018 weld metal, Fis..re 2. No stress-corrosion failures have been observed
in the 5Ni-Cr-Mo-V base metal or in the experimentz.l MIG weld metal after 10
months exposure in a marine atmosphere or in sea water. In general then,
the 5Ni-Cr-Mo-V weldment should be as resistant to various types of corrcsior
as an HY-80 weldment.
"To date, three 80-ton heats of the 5Ni-Cr-Mo-V steel have been
melted in standard electric furnaces using a conventional double-slag
process, and the composition limits have been met with no particular
problems. The desirability of melting the steel by the basic-oxygen process
and by vacuum-consumable-electrode remelting is now being evaluated. In
addition, the advantage of ,icuum-carbon deoxidation after electric-furnace
and after basic-oxygen melting is being assessed. The steel has normally
been air-cast in the same size ingot molds as those used for HY-80 steel.
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To date, most of the 5Ni-Cr-Mo-V steel production plates have been cross-
rolled to a ratio of 3 to 1 or less. Laboratory studies indicate that
directionality of properties can be satisfactorily minimized for cross-
rolling ratios of 8 to 1 or lower, Table II. The limitations that this
proposed maximum cross-rolling ratio may impose on production rates and
plate sizes are now being developed. The 5Ni-Cr-Mo-V steel production
plates have been heat-treated on conventional facilities with no special
problems. Because the steel was designed to exhibit a constant yield
strength when tempered in the range 900 to 1100 F, no difficulties have been
encountered in producing the steel with a 15 ksi yield-strength range,
Figure 3.
Several CB-103 structural sections of the 5Ni-Cr-Mo-V steel have
been rolled with no apparent difficulty, and the properties after heat
treatment were very attractive, Table III. A large ingot of the 5Ni-Cr-Mo-V
steel was forged into a ring with no difficulty, and 5Ni-Cr-Mo-V steel
castings as large as 500 pounds have been produced. The properties of the
laboratory castings were quite satisfactory after heat treatment, Table IV.
Cost estimates for producing a large 5Ni-Cr-Mo-V casting of the type used
in HY-80 hulls have been received from approved HY-80 casting producers.
The production and evaluation of one or more large 5Ni-Cr-Mo-V steel castinga
should establish the status of the casting development.
Although an exact price for 5Ni-Cr-Mo-V steel plates must await
a specification based on additional production experience, the price will
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probably be about that of HY-80 steel on a strength to weight basis. Trial
orders for plates and shapes will now be accepted in accordance with ncrmal
delivery sched~iles.
Joining Development
The strength, toughness, crack susceptibility, and transformation
characteristir-s of the heat-affected zonc was a prime consideration in the
developirent of the ccmposition of tht 5Ni-Cr-Mo-V steel. When the steel is
weldedI over t wide range of practical heat inputs and preheat and interpass
temperatures. the heat-affected-zone hardness is almost identical to that of
the base metal. This is an improvement over HY-80 steel. With the same
welding c-'nditions, the heat-affected zone is essentially fully martensitic
and the minimum Charpy V-notch energy absorption is about 80 ft-lb at 0 F,
Figure 4. T1he heat-affected zone of the 5Ni-Cr-Mo-V steel, as measured in
very critical laboratoryj" tests, is about as resistant to restraint crarking
a3 the most crack-resis'ant :IY-80 steel, Table V. Thus, the procedures nCw
employed to insure sat _-,,_or' heat-affected-zone properties in HY-80 steel
weldments should b; satisfactory for SNi-Cr-Mo-V steel weldments.
f.,r tte past y"ear, ever half the HY-130/150 program effort ha3 been
devo•',d to the development of filler metals and welding techniques. A MIG
filler metdl ft the composition shown in Table VI has been developed that has
.xc•-plpional tcujhness at an average yield strength of 136 ksi when deposited
by spray transter Techniques have been developed so that similar properties
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are obtained when this filler metal is deposited in the vertical or
overhead position. To date, commercial quantities of this filler wire have
not been produced because studies have been in progress to develop a higher-
strength weld metal.
Evaluation of 2Mn-2Ni filler metals designed to exhibit weld-metal
yield strengths cver 140 ksi has shown that these weld metals are suscep-
tible to cracking. Increases in preheat and interpass temperature have
reduced the cracking but have also reduced the yield strength. For that
reason, major modifications in the composition of experimental MIG filler
metals are now being examined. Thus, the development of a practical MIG
filler metal with a yield strength of 145 to 150 ksi is not expected for
about 6 months. However, as discussed under Structural Evaluation, the
present 138 ksi average-yield-strength weld metal may be suitable for an
HY-130/150 weldment. at least on an interim basis. Therefore, a production
heat of the 2Mn-2Ni Mýý' filler wire is being made.
Because preliminary tests of 5Ni-Cr-Mo-V weldmenta fabricated
using covered electrudes were promising, development of experimental
HY-130/150 ccvered electrodes haz been continued on a high-priority basis
and is being further accelerated. The best weld-metal properties that have
been obtained to date when plates of the 5Ni-Cr-Mo-V steel were welded under
practical conditicns -. sing covered electrodes are shown in Table VII.
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7klthough the weld metal exhibits a relatively high yield strength, the
touqhness is lower than that desired. Explosion-deformatien tests to
evaluate the most promising compositions are planned for the immediate
future. Final selection of the most promising covered electrode is
scheduled for May 19,5. Shortly therea.fter, prcduction quantities c¢f the
best HY-130/150 covered electrode should be available for fuli-scale
evaluat ion.
Structural Evaluation
From Laboratory studies on the 5Ni-Cr-Mo-V and other high-
yield-strength steels, a method has been devised for predicting the coId
formability of steels from their tensile ductility. Laboratory forming cf
plates up to 1/2 inch thick and bhipyard forming of plates up to 3-3/8
inches thick, Table VIII, have confirmed the prediction equation. The tcs-_
results also showed thlit ,N'-Cr-.M-,-V steel plates have more than en'qugh
duct i it yt .tc be coi d -f rrr.d ! o"d Idi rr.ch sma IIer than th,_-se required for
submarine-hull tabricat il?. 1the effect of cold forminq cn the- mechanical
properties vf hiv,'-.qP, ,, 5-Cr-Mu-V steel plates is currently bt.ing
evaluated, 'in6 the W'e1u1 4 be ,x-,.xnparv-, with thosc .-,t proviously cro-
pltted itmi lar study r.n HY-HO steel.
A marIr s o.f:dy ,• the s'r-ictural nuitalility of 5N, -Cr-Mo-V stc-l
plat,, .ind "'ld.•unt h.as b I. j. [lanr.d .is descritibed in Appendix A. The
,ud%*v i L:'erd'-d IF. k,. nntr..,t the s-Jitablit, •f 5Ni-Cr-Mo--V weldments
UNITIED STATES STIEEL
for the fabrication of a prototype structure. Tht tests will be cond,,cted
by the Applied Science Laboratory, the Marine Engineerinq Labcoratory, the
Naval Research Laboratory, and the Contractor. Irhi. Weldmer.t Evaluation
Program is schedu± ,d to be initiated around January 1, 1905. However, the
program cannot be initiated until a filler metal meeting most of the ulti-
mate requirements is selected. That selection, in turn, cannot oe made
until the yield-strength requirements for the filler metal as compared with
those for the base metal have been defined.
To investigate the effect of yield-strengtn differences between
the weld metal and base metal, 1-inch-thick plates of the 5Ni-Cr-Mo-V steel
having nominal yield strengths of 130, 140, and 150 ksi were joined with a
2Mn-2Ni MIG weld metal having i nominal yield strength of 140 ksi. The
weldments were explosively deformed by four 7-pound shots of pentfclite.
After each shot, the thicknesfr reduction in the bulge area was measured.
The results, Figure 5, showed that each of the weldments reduced in thick-
ness 12 to 14 percnt without cracking. This ability to deform exten'ively
at high strain rates is extremely encouraginq.
Figure 5 also shows that the thickness reduction of the base
metal generally decreased as its yield strength increased. whereis the
thickness roduct ion cf the weld metal was about the sa-me for the thr.e
weld-ents. Thus, in the maximum bulge are;%. Curve A shy.s ,haz. the weld
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metal reduced or thinned less than the base metal because its yield strength
was higher than that of the base metal, Curve B shows that the weld metal
reduced abcut the same amount as the base metal because their yield
strengths were about equal, and Curve C shows that the weld metal reduced
-ore than the base metal because its yield strength was lower than that of
the base metal. These results indicate that, to a limited extent, the
deformation across thc weld depends upon the relative yield strength cf the
base meta] and the weld metal. in general, an undermatching wel! metal
(Curve C) is undesirable because the weld metal, which is usually less
tough and ductile than the base metal, is deformed more than the base metal.
However, the cifference between the overmatching (Curve A) and matching
(Curve B) conditicns appears insignificant. In both instances the weld
metal undergoes almost as much deformation as the base metal. Thus for the
conditions studied, the deformation characteristics of a weldment with a
matching filler metal are about as desirable as those of a weldment with an
overmatching filler metal.
When applied to the 5Ni-Cr-Mo-V experimental HY-130/150 steel and
experimental HY-130/150 MIG filler metals, the preceding observations indi-
cate that a matching cr overmatching weld metal is desirable when its duc-
tility and toutjhness are about equal to those of lower-strength weld metal.
Unfoitunately, experimental overmatching weld metals have exhibited a high
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susceptibility to cracking. Thus, at the present state of development, a
matching 5Ni-Cr-Mo-V weldment will outperform an overmatching weldment at a
base-retal yield strength of 140 ksi.
The explosion tests indicate that a satisfactory weldment having
a yield strength of 140 ksi appears essentially developed. Although this is
correct on an absolute-yield-strength basis, it is not correct on a minimum-
yield-strength basis. To insure a minimum yield strength of 140 ksi, HY-1401
plates would be produced to yield strengths in the range 140 to 155 ksi.
Thus, to match the average yield strength of an HY-140 base metal, the yield
strength of the weld metal should average about 148 ksi.
Currently, the yield strength of a high-reliability high-toughness
weld metal is about 138 ksi. This weld metal would match the average yield
strength (138 ksi) of HY-130 production plates (yield-strength range of 130
to 145 ksi). Thus, to facilitate work on the Weldment Evaluation Program,
a 130 ksi minimum-yield-strength weldment is recommended as an interim
objective. No difficulty is anticipated in lowering the yield-strength
range for the 5Ni-Cr-Mo-V steel from 140 to 155 ksi down to 130 to 145 ksi.
However, studies to develop weld metals having higher yield strengths would
b4' continued at the current rate of effort so that the minimum yield strengtt
could be set at 140 ksi when the higher-strength weld metals become
available.
Setting the minimum-yield-.strength objective for an HY-130/150
weldment at 130 ksi would also facilitate an increasein the plate-thickness
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ob]ectives from the present average and maximum thickness of 2 and 4 inches,
respectively. The composition of the 5Ni-Cr-Mo-V steel was carefully de-
signed so that the optimum combination of mechanical properties and welda-
bility was obtainable in 2-inch-thick plates, the thickness of primary
interest. Thus, the mechanical properties of 3- to 4-inch-thick plates are
somewhat lower than those of the 2-inch-thick plates. This loss has not
been considered important because the heavy plates are used in noncritical
locations or the components are designed to compensate for the lower proper-
ties. If, however, the interest in increasing thickness continues and 3- to
4-inch-thick plates represent the thickness of primary interest, adjustments
in the composition of the 5Ni-Cr-Mo-V steel should be made so that the opti-
mum combination of mechanical properties and weldability is obtainable in
3- to 4-inch-thick plates. Much more development work would be required to
make the required composition adjustments at a minimum yield strength of 140
ksi than at a minimum yield strength of 130 ksi. For that reason, the pro-
gram to evaluate the structural suitability of weldments having a minimum
yield strength of 130 ksi, including heavy-gage weldments, could be initiated
without significant delay, whereas some delay is anticipated in initiating
a similar program for 140 ksi minimum-yield-strength weldments.
Finally, the higher toughness that has been observed for the 5Ni-
Cr-Mo-V steel at a yield strength of 130 ksi compared with that at a yield
strength of 140 ksi (102 ft-lb versus 80 ft-lb for 2-inch-thick plate) may
be desirable, particularly for the very heavy plates required. This
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observation is based on the amount of base-metal shear tearing that has
occurred in explosion-bulge tests of 140 to 150 ksi yield-strength 5Ni-Cr-
Mo-V weldments. Despite the very high toughness of the 5Ni-Cr-Mo-V steel
compared with the minimum objective of 50 ft-lb, the shear tearing is much
gi.dcter than in HY-80 steel. This is not unexpected inasmuch as the stored
elastic energy to propagate cracks is much higher in the 5Ni-Cr-Mo-V steel
than in the HY-80 steel, whereas the shear energy absorption of the 5Ni-Cr-
Mo-V steel at a minimum yield strength of 140 ksi is lower than that of HY-
80 steel at a minimum yield strength of 80 ksi. (When HY-80 steel is heat-
treated to a yield strength of 140 ksi, its shear energy absorption is only
about one half that of the 5Ni-Cr-Mo-V steel at the same yield strength.)
Although the resistance of HY-80 steel to shear-crack propagation may be
greater than that requized for a "fracture-tough" design, the higher tough-
ness of a 130 ksi compared with a 140 ksi minimum-yield-strength 5Ni-Cr-Mo-
V steel may ultimately be desirable for the low-hull-fraction high-toughness
combatant submarine.
For high-hull-fraction submarines and for noncombatant sub-
mersibles, the preceding discussions are probably not applicable. In fact,
undermatching weld metals are believed to be quite satisfactory because the
total strain imposed upon the weld mr.tal, even in areas of high strain
concentration, is far less than that produced in explosion tests. Thus,
submersibles of this type fabricated from the 5Ni-Cr-Mo-V steel could
probably he designed to a minimum yield strength of 140 ksi and higler.
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Prototype Evaluation
If the minimum yield strength for an HY-130/150 weidment is set
at 130 ksi, at least on an interim basis, the Weidment Evaluation Program
can probably be completed in time to initiate the Prototype Evaluation
Program during the latter part of 1965.
HY-180/210 Program
Because the HY-180/210 program is a feasibility study, which
would be followed by a development study, the progress of the program can
best be assessed by evaluating the probability of successfully developing
the approaches that have been investigated.
Base-Metal Development
Three different alloy-steel systems have been systematically
investigated to determine their potential as HY-180/210 base metals- (1)
conventional quenched and tempered carbon-martensitic steels, (2) very low-
carbon mar aging steels, and (3) carbon-martensitic precipitation-hardened
steels. The strength-toucghness relations that have been exhibited by 1/2-
inch-thick plates from laboratory heats of the various steels are summarize
in Figure 6. The summary shows that mnaraging steels consistently exhibit
the best. comibinat ions of strength and toughness.
The opt imum trend line in Figure 6 shows that for the current
state cf development, the highest toughness is about 64 ft-lb at a yield
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strength of 185 ksi, the lowest-aim yield strength for production plate]
to insure a minimum yield strength of 180 ksi. The trend line also shows
that the toughness decreases about 1 ft-lb for every 1 ksi increase in the
yield strength. The optimum trend line is based on the properties of
laboratory heats that were melted in vacuum so that the interstitial gas
content (02, H2 , and N2 ) and the metalloid content (C, P, and S) were very
low. In addition, the small laboratory ingots solidified much more rapidly
than large production ingots and thereby minimized segregation and the size
of the ingot dendrites. When heats of the 12Ni-5Cr-3Mo steel were melted
in air in a 20-ton electric furnace and air-cast into 32- by 60-inch, 20-
ton ingots, the properties fell significantly below the optimum trend line,
Figure 7. At this time, the relative effects on mechanical properties of
steel purity as controlled by melting practice and of segregation and ir-got
structures as controlled by ingot size are not known. Large-size heats of
the l2Ni-WCr-3Mo steel are ncw being melted by various low-residual-element
practices so that the effect of melting practice can be assessed for large
heats and ingot sizes.
As discussed herein under the HY-130/150 program, resistance to
shear-crack piopagation undoubtedly decreases as yield strength increases
at a constant toughness because of the increase in the stored elastic
energy with increasing yield strength. Thus, the development of melting
practices for large heats that would insure cnnsistent attainment of the
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optimum trend line in production plates may not assure fracture-tough
behavior in large fabricated structures. For that reason, research must
be continued on alloy systems that are inherently tougher than those
developed to date. In addition, work should be continued on melting
practices that may lead to even lower residual-element levels in high-
yield-strength steels with the objective of further increases in tcughness.
Figure 7 also shrws that the toughness of the l2Ni-SCr-3Mo steel
is significantly lowered as the plate thickness increases. The same effect
is expected for all alloy s,'stems at a yield strength in the range 180 to,
210 ksi. To confirm this observation, heavy plates rolled from producticn
heats of the most promising quenched and tempered steel and of the most
promising carbon-martensitic precipitation-hardened steel will be evaluated
Because the thick plates that are required for combatant and nonccirbatant
submersibles appear to exhibit much lower toughness than thin plates.
methods (,f minimizing or eliminating this effect. must be devised. Figure 8
shows that the loss in toughness in thick plates can be minimized in the
12Mi-5Cr-3Mo steel by forging rather than rolling the plates. Forging
Lncieas.-d the amcunt and depth of hot work and decreased the temperature
range of hot workini. thezeby increasing the toughnes_ýl of thick plates.
Further work on special hot-working techniques will be required.
I'',:e~cnts in properties that can be achieved by other special
-, "-:uquts ret-t be exploro*d. One extremely promising technique
U#4UO STATES ST L
that was originated about 4 years ago at the Applied Research Laboratory
is being intensively examined in the HY-180/210 program. The technique
involves rapid heating during austenitizing to produce a very-fine-grain,
heterogenecus austenite. When conventional carbon-martensitic steels are
austenitized in this way, very significant improvements in the strength-
toughness combinations have been obtained, as illustrated in Figure 9 for
the 5Ni-Cr-Mo-V steel. studies are r.'v being planned to determine (1) the
maximum plate thickness at which such improvements can be obtaired, (2) the
applicability of rapid heat treatment to alloy systems other than quenched
and tempered steels, (3) the effect of the composition of quenched and
tempered steels on response to rapid heat treatment, and (4) the fea-
sibility of designing and constructing production facilities for rapid
heat treatment of large thick plates. Work on this and other special
processing techniques shculd be accelerated.
The development :f imprcved HY-180/210 alloy systems, improved
low-residual melting and casting techniques, improved methods of hot
working, and special processing techniques such as rapid heat treatment
may not insure the development vf plates that can be fabricated into a
fracture-tough structure, Therefore, studies should be initiated to
establish the extent to which improved design, fabrication, and inspection
can reduce frac~ure-to'qhness requirements. At present. submarine hulls
are fabricated from weldments that are tough enough so that large fiaus
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and high stress concentrations do not cause crack extension until stresses
close to the ultimate tensile strength are imposed. Inevitably, a yield
strength will be reached at which the steel will no longer exhibit
fracture-tough behavior as previously defined. At present, steels do not
exhibit this type of fracture toughness at a minimum yield strength of 180
ksi. Thus, designs for submersibles will eventually be required that
minimize stress concentrations and in which the stress concentrations
caused by geometric discontinuities or "hard spots" can be accurately
analyzed. Fabricatiolt Lechniques that minimize or eliminate stress concen-
trations, residual stresses, and flaws must be developed, evaluated, and
applied. Finally, inspection techniques nr st be devised, evaluated, and
utilized that will detect all flaws larger than those that will propagate
catastrophically in material of a given fracture toughness.
As was previously observed, stress corrosion :s not exiected to
be a problem in the HY-130/150 steels. However. signiflcadt suiceptibiliti
to stress corrcsion has been observed in quenched and tempered steels
having yield strengths ever 200 ksi. Thus, the yield strengths of
1Y-180/210 steels !it in a 'jraý area" where stress corrosion may ci may
not be a problem. Prel~minary tests indicate that the 12Ni-SCr-3Mo base
metal may also be susceptible to stress corrosion and that the experimental
filler metals devcloped to date for the 12Ni-WCr-3Mo steel probably are
susceptible to stress cc:rosion, Figure 10. Thus, the 180 to 210 ksi
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yield-strength range appears to be a "gray area" for stress corrosion of
martensitic steels. The factors influencing stress corrosion of steels in
this yield-strength range are being intensively investigated with the aim
of developing composition or processing modifications that will eliminate
stress-corrosion susceptibility. Preliminary results indicate that fine-
grain steels are much more resistant to stress corrosion than coarse-grain
steels. Thus, the ultrafine grain size produced by rapid heat treatment
may eliminate stress corrosion in experimental HY-180/210 steels. However,
consideration should be given to systems for protecting the weld metal and
possibly the base metal in HY-180/210 submersibles.
Joining Development
Because some experience with the production of the l2Ni-5Cr-3Mo
steel was available at the time the Contract was initiated, the weldabil;tý
and filler-metal development in the HY-180/^10 feasibility study have been
concentrated on maraging steels. Studies of the heat-affected-zone --
erties of the 12Ni-SCr-3Mo steel have shown that the steel is reasonably
resistant to restraint cracking and that the strength and toughness C' the
heat-affected zone can be restored to essentially that of the base metal
by a 900 F postweld aging treatment. Table IX.
Numerous filler metals of the 12Ni-SCr-3ho type have been
evaluated when deposited by the RIC and TIG processes. In general. rno
dafficulty has been encountered in fabricating sound 3oints or in obtainir-
-19-
U~riED STAlKS STEEL
the desired weld-metal yield strenyth. However, as shown in Figure 11, the
toughness of the weld metals, particularly those deposited by the MIG
process, is rather low. The optimum trend line indicates that a toughness
close to 50 ft-lb at a yield strength of 185 ksi should be attainable with
the :2Ni-SCr-3Mo type filler metal.I after suitable additional development
wo~t. Figure 11 also shows that several oarbon-martensitic precipitation-
hardening weld metals exhibit strength and toughnes;s combinations close to
the optimum trend line. Thus, there is reason to believe that WH-180,'210
filler metals will ultimately be developed that will be almost as tough
as an HY-180/210 base metal. Moreover, the loss in toughness that is
observed when the thickness of the base metal is increased is not a
factor in the toughness of the weld metal. inasmuch as the weld metal is
deposited in essentially the same way regardless of the plate thickness.
As was obsvrved for the HW-!80/210 base metal, an energy absorp-
tton of d% ft-lb ror an HY-h8O/21O weld metal may not insure a 'fracture-
strio-tur#,. Theretore. tbhe( o'iments concerning the need for studies
o, improved dv~iqn. fabrication techrxques. and inspection techniques to
munni1:e tou4hnt't*s r.,-i re.wnents for I'-iO:2O batse metals apply equally to
yY- 8O 210 weld IJ A.
-h," r,'•.l• I ,,. - IIY-l S2O study zndicate th.vt it is feasible
to dev,. lop a•e•-l wel.ents havit.q yield strenq-=h- in the ranqe 180 to 210
kri. th,! exht bhe-i-vil ard weld-mtal Charpv V-notch ener(w.' absorptions
L041TEO STATES STEEL
of about 50 ft-lb. However, the base metal will undoubtedly be melted to
very low residual-element levels, and the ingots will be processed to
plites by special techniques. In addition, other special processinq tech-
niques will probably be employed to insure a consistently high toughness.
Similarly, the filler metals %ill probably be produced to very low residual
element levels, drawn to wire by speciai 'echniques, and deposited only by
processes that insure retention Pf tic ".gh purity. To succeed tn this
undertaking, a significant develcpment program will be required.
Initially, the cost of a high-toughness HY-180/210 weldment will
be high. Hu*'ever, the material, fabrication, and inspection costs should
decrease steadily as experience in this frontier area is gained.
-21-
UNITEO STATES ST11L
References
1. L. F. Porter, A. M. Rathbone, S. T. Rolfe, and A. Leszewich,"Prelimina ry Status Report: Development of an HY-130/150 Weld-motQ" Applied Research Laboratory Report 40.18-001(6), (S-10000),May 31, 163.
2. J. H. Gross, "Hiqher-Strength Steel Weldments for Submarine Hulls -
An Interint Status Repnrt," Applied Research Laboratory Report40.018-001(20), (S-iXOQCO), April 1, 1964.
-22-
UNITED STATES STEEL
APPENDIX
-23-
UNITED STATES STEEL
APPENDIX A
Proposed Weldment Evaluation Program for
5Ni-Cr-Mo-V Steel
I. Welding Procedure Study-Part I (U. S. Steel)
A. Purpose: To define limits of plate thickness and preheat
temperature within which suitable mechanical properties and
soundness can be achieved.
B. Test Outline: Experimental weldments will be fabricated
as follows:
Plate PreheatThickness, and Interpass Temperature,
inches Welding Process F
1/2 Covered Electrode 150, 200, 250, 3001/2 MIG 150, 200, 250, 300
1 Covered Electrode 150, 200, 250, 3001 MIG 150, 200, 250, 3002 Covered Electrode 150, 200, 250, 3002 MIG 150, 200, 250, 300
C. General Test Conditions
1. All weldments to be 18 inches wide by 18 inches long.
2. All weldments to be radiographed and tested in theas-welded condition.
3. Welding heat input:
a. MIG - 1/16-inch-diameter electrode - 60,000 +5000 joules/inch.
b. MIG - 0.045-inch-diameter electrode - 45,000 +5000 joules/inch.
(Continued)
-24-
UNITED STATES STEEL
APPENDIX A (Continued)
Proposed Weldment Evaluation Program for
5Ni-Cr-Mo-V Steel (Continued)
c. Covered Electrode - 3/16-inch diameter - 45,000 +5000 joules/inch.
d. Covered Electrode - 5/32-inch diameter - 30,000 +
5000 jcules/inch.
4. Joint Geometry - 1/2-inch-thick plate - 600 single Vee,1- and 2-inch-thick plate - 600 double Vee.
5. MIG shielding gas = A + 202 at 50 cu ft per hour.
6. Covered-electrode conditioning: All electrodes bakedat 800 F for one hour and stored at 250 F prior to use.
7. Mechanical-property tests:
a. All-weld-metal 0.252-inch-diameter tension tests.
b. Charpy V-retch impact tests at +80 F, 0 F, and-60 F.
c. AWS side-bend tests.
d. Transverse plate-type tension tests (Fig. 2,MIL-STD-418).
II. Welding Procedure StdýFart IT (U. S. Steel)
A. Purpose: To eetermine effects of stress relieving on weld-metal mechanical properties.
B. Experimental Procedures
1. Two weldments - 1 inch by 12 inches by 40 inches (40-inchweld) - one tc be fabricated by the MIG process, the otherby the covered-electrode process. The welding conditionsto be determired from results of Fart t.
(Continued)
_-25-
UNITED STATES STEEL
APPENDIX A (Continued)
Proposed Weldment Evaluation Program for5Ni-Cr-Mo-V Steel (Continued)
2. Test conditions:
,I. As-welded.
b. 1025 F for 1 hour, slow-cool at 50 F per hour.
c. 1025 F for 1 hour, accelerated air-cool.
d. 1025 F for 1 hour, accelerated air-cool, repeatfor 10 cycles.
e. 1025 F for 100 hours, accelerated air-cool.
3. Mechanical-property tests:
a. All-weld-metal 0.252-inch-diameter tensiontests.
b. Charpy V-notch impact tests at +80 F, 0 F, and-60 F.
III. Welding Procedure Study-Part III (U. S. Steel)
A. Purpose: To determine relation between weld cracking andpreheat and interpass temperature.
B. Test Outline: The following specimens will be fabricatedwith both the MIG and covered-electrode welding processes.The welding conditions will be determined by results ofPart I.
1. Electric Boat frame-to-hull specimen:
a. 200 F preheat and interpass temperature, inspectin as-welded condition.
(Continued)
-26-
UNITED0 STATES "TEEL
APPENDIX A (Continued)
Proposed Weldment 3valuation Program for5Ni-Cr-Mo-V Steel (Continued)
b. Preheat and interpass temperature based on resultsof first specimen, inspect in as-welded condition.
c. Preheat and interpass temperature that does notproduce weld cracks in as-welded condition, inspectin stress-relieved condition.
2. Lehigh restraint-cracking-test specimen:
a. Single-pass welds with different restraint at 78 F.
b. Single-pass welds with different preheat temperatures.
c. Double-pass welds with different preheat temperatures.
IV. Fracture-Toughness Studies
A. U. S. Steel:
1. Drop-weight tear tests (1-inch. and 2-inch-thick plates).
2. Drop-weight bulce tests (1/2-inch plain plates andweldments).
3. Plain-strain KIC tests (1-inch and 2-inch-thick plates).
8. NRL:
1. Drop-weight tear tests (1-inch-and 2-inch-thick plates).
2. Drop-weight bulge tests (1-inch-and 2-inch- (if possible)thick plain plates and weldments):
a. Plain plates (NDT. FTE. FTP).
(Continued)
-27-
UNrIO WfAT $TO=
a
APPENDIX A (Continued)
Proposed Weldment Evaluation Program for5Ni-Cr-Mo-V Steel (Continued)
b. Weldments (with and without crack starter):
1. MIG and covered electrode.
2. As-welded plus stress-relieved.
3. Selected preheat and interpass temperatures,and heat inputs based on results of weldingprocedure studies.
c. Matching, undermatching, overmatching:
1. +30 F with photogrid.
2. 140 ksi welu nketal.
3. 130, 140, 150 ksi base metal.
3. Explosion-deformation tests (1-inch-thick plain platesand weldments - conditions same as those used for drop-weight bulge tests).
4. Explosion-tear - establitsh flaw size - deformation
relationships.
C. ASL:
1. Explosion-bulqe weldment tests (2-inch-thick):
a. MIG and covered electrode
b. As-welded plus stress-relieved.
C. Welding conditions based on results of welding
prccedure studies.
(Cont i nued)
_ _ _ _ _ _ _ _ -28-UNITED STATES STEOL
APPENDIX A (Continued)
Proposed Weldment Evaluation Program for5Ni-Cr-Mo-V Steel (Continued)
V. Fatigue Studies
A. U. S. Steel:
1. Cantilever beam - plain plate and weldments.
2. MIG and covered electrode.
3. Surface conditions (smooth, notched, sand-blasted).
4. Air and synthetic sea water.
5. Strain ranges to produce failure between 1O2 and 105
cycles.
B. NRL:
1. Rate of fatigue-crack-propagation tests.
C. MEL:
1. Welded box tests.
2. Programmed axial tests.
D. ASL:
1. Large plate tests.
2. Large plates with fillet welds.
R. University of Illinois - Axial tests (limited number of teststo be conducted as part of existing Bureau of Ships contractwit: University of Illinois):
(Continued)
-29-
U0T41D *TAM STEEML
APPENDIX A (Continued)
Proposed Weldment Evaluation Program for5Ni-Cr-Mo-V Steel (Continued)
1. Plain-plate specimens.
2. Transverse butt-weld specimens.
VI. Corrosion Studies (U. S. Steel)
A. Stress-corrosion (U-bend, 16 percent strain plus yield-stressloading), galvanic-corrosion, and general-corrosion specin,ans.
B. MIG and covered-electrode weldments.
C. Exposure - Wrightsville Beach and Kure Beach, N. C.:
1. Flowing sea water.
2. Nonflowing sci water - total immersion.
3. Nonflowing sea water - periodic immersion.
4. Marine atmosphere - 80-foot lot.
-30-
UNIT9D STATES STEL
; -,jwo00
q' .•"° 0o.lOim •" mi.-. mn.-
0 0 0
W. I.. .
r0 0 cwIm >Pt v¶ ¶ 0 -01
w. .-c .o* o -* -
A ""' * al •oI@' P
,• , • - 1.4 I
ISO. tO rt
w kA ow 0
rt
0 0 9V 0.
v n
1.-. 0 0 1
C0 $0 0 n
o nw!~ 130 0 4
4 0. 0 0'0 JU ttAU
0. C) W 40
0 Lo
%A 0
3% rtt
rt rt r' 0 0rt f t0 0 0 I
o o 0..- - w
0 0.
0~ 00 0 1
1W CI,
JD CD. 0 0~SM U
0
0 -
Z~~w 0 ~4 -~ . '!U O0 * S..PQ
it
0
:3 rt
I3 M 0 0P3~
000 it m o
,.io n1 :3 " : 3 -F Q r~p Q :1 4 a
I- V, ". -f P.
0C F t fr~ r~t < t rDo r-. lb0 c t*
0. ri 0.o. to p - 09
et
c-
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0 ON b-a ~~w(I to 0 1-4* 'J$ r9~t *0
-4 0 14'. 0 4w 0 to x -
* - ,t -J'31
.4 0- -0t
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S ~CI, frNtJ j t%~j I '! 0ý:
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11.&
I
Table IV
Mechanical Properties of 5Ni-Cr-Mo-V Cast Steel Plate
Test Specimens were loc7atedat Mid-Length of 4- hy ?2- by 12-Inch-Plate Casting
____Riser
61"
Yield Strength Elongation Charpy V-NotchSpecimen (0.i/ Offset), in 1 Inch, Energy AbsorptionLocation ksi % at 0 F, ft-lb
1 147 6.0* 712 147 18.0 733 148 17.0 754 148 17.0 765 147 18.0 666 147 17.0 65
*Sand inclusion.
NOTE: Casting was homogenized at 1700 F and water-quenched.Austenitized at 1500 F, 2 hours, wU~er-quenched.Tempered at 1080 F, 2 hours, water-quei _'hed.
(40.018-001) (39)
UNITED STATES STEEL
tJIt
Mz0 U)
0 0 rt w
(D' m 1
00 P--
'-a 10 uIt
cn i-' 0 0 rtO i-NV phL)t- iO wt
(D~
ODD
rtr
CD HZC
P- A 1 (0 CD (D
*t xi
H H- Ht L.' V
(D m 0
0- A 0000C0000l00 0 100000 tvI0
CA~~r P.F J
0i
o of
c -O(n ms-3 :3
rtQ
Do
Cfl (D 0h
0 H i0
U4 OD~I 0L.J 1~C - (A 0)
0 1'- (D0t 0
00
0 0 (1
Il LaL (DPi D L
w 00
o
0 1
0 0
OD 0)
00
Iftj0
02 (1
020
0C
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rt
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0 0J0 (D
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0 ,
0)
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hi '0 00 0~""
0
hi C,w 0
Table VIII
Comparison of Predicted and ObservedMinimum Bend Radii for 5Ni-Cr-Mo-V Steel
Plate Predicted Minimum Actual InsideThickness, Inside Bend Radius, Bend Radius
-. xjghrg inches at Cracking, inches
1/4 0.4 Between 0.19 and 0.34
3/8 0.7 Between 0.23 and 0.53
1/2 0.9 Between 0.78 and 0.94
1 1.8 <1.8
2 3.6 3.1
3-3/8 6.1 -(5.1
(40.018-001)(39)
UNITED STATES STEEL
w BI 0 - NJ OW X ' 0*Mh 0 0 0 0 0 0 0 0 mS-~0 0 0 0 0 0 0 0 0
0 0 0Xrt rt
10
0 0
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rt
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4~r ft :f> 0 : cm
0 ortrft H4
rttUX
00
Lj 00 .irt .
4A m 0~ m. A J LA % k
RATIO OF TOTAL STRAIN RANGE AT FAILURE TO YIELD STRAIN
Clo0 0 00a00- -
-0 30 0 S 0 7 O 0
II
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S• METAL
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0-I
BASEw METAL
HY-80 STEEL 5 Ni STEEL
or x
g0
zU 4-
500
SMAXIMUM
AVER AGE
I--MINIMUM
400
CORROSION POTENTIALS OF HY-80 STEEL AND 5 Ni - Cr-Mo-V STEELIN SYNTHETIC SEA WATER AT ROOM TEMPERATURE
DRAWNM 14VIY oI By A,10OVo UY.,. Do'se0 'Ll~o W.UNITED STATES STEEL CORPORATIONDRAWING 40 PJdcf No NO.
40 O.e1 001(30 APPLIED RESEARCHARL 18-492 Hu/ AZ! PrTSBURGH. PA. 2
6-14"t Sf v. M
160-2- INCH-THICK PLATE
(HEAT NO. X53588)
I0'-U.0
ag
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110-
As 1N900 1000 1100 1200QUENCHED TEMPERING TEMPERATURE, F
TEMPERING CURVES FOR 1/2- AND 2-INCH-THICK PLATES OF 5Ni-Cr-Mo-VSTEEL (MIDTHICKNESS LONGITUDINAL PROPERTIES)A.WN ov CHKID sy ,,.,omovigo ov'COPRTN
A.R. L .J. W J.,.o. UNITED STATES STEEL CORPORATION FIGUREO.wi "--- _"X'"4lo~ APPLIED RESEARCHN,
ARL 18-484 ,, P",URGH. PA.n n n 3
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o x 0
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BASE METAL WELD METAL BASE METAL
14 1-
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CURVE A2 0~VERMATCH/\
S. 8 VI0
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14C
4ý- BY 1
NUMBERS 'C*Tc v1'E U'C S.TRENGT4 OF2~~ 1~BSE YVE%- .. 3M' AND WELD METAL IWMI IN KSI
C'STANIcE FRV CIEN2"RL' OF *%J'ýýe
EFFECT OF DIFFERENCE IN YIELD SrRENG"TH OF 5 N C r-Mo 'v S rEEL AYJD2 Ni MIG WELD METAL ON EXPLOSION - DEFORW~lON CHAR44CTERI'S'TIS
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A- CARBON-MARTENSITE PREC,PITATION-HARDLNED90-
so- OPTIMUM TREND LINE
0
0Q A
z£ A
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YIELD-STRENGTH -NOTCH - TOUGHNESS REL"T:3N FOR EXPERIMENTALHY-180/210 LABORATORY STEELS
IMAN V 04 0By APPOOV10 IRV IJiAoso j m G UNITED STATES STEEL CORPORATIONR I.MUOfAAWiftG No ;7 6CmeNO.DARL 848 P.1C14P0 APPLIED RESEARCH
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z 2 -ihNCH %
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Ui30-
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-0- ESTIMATED STRENGTH-TOUGHNESS RELATIONFOR INDICATED PLATE THICKNESS
0 _ I170 180 190
YIELD STRENGTH (0.2% OFFSET, ksi
YIELD STRENGTH AND NOTCH TOUGHNESS OF PLArES FROM20-TON HEATS OF 12Ni-5Cr-3Mo STEELS
RAWN , , 0 CHKI' AD NOVh'O UY 1G
GA.Z 0.S;.D _J.H~._.G JUNITED STATES STEEL CORPORAT'ON FIGURE
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a-h22 t. 106!
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S40- 8-INCH-THICK FORGED SLAB
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YIELD STRENGTH (0.2% OFFSET), 4s,
YEL--STRENGTH-NOTCH-TOUGHNESS RELATION
ROLLED AND FORGED T2Ni-ECr-3Mo STEELDRAWN Y J C |-- Pei4"OV' .o UY .. . .. . . . .....GA.4J.G._6 ,•UNITP!3 ...TATF=: t."-,, ...... UR
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YIELD STRENGTH, kil
I I YIELD -STRENGTH -NOTCH TOUGHNESS RELATION FORRAPIDLY HEAT-TREATED 5 Ni-Cr-Mo-V STEEL
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A L 8. :i/i4;64 PITTS _URGH. PA.•1 I 489 " 1 I _ I II I
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Figure 10. Stress corrosion cracking in 12IM-Cr-31o weldmetal (bead-on-plate U-bend specimen). Picral
UNITED STATES STEEL
o C N E E
o CARBON-MARTENSITE -MIG
0 CARBON-MARTENSITE N -IG
70 A MARAGING -MIG
?or & MARAG ING - T I G
OPTIMUM TREND LINE
Y0e A A
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YIELD- STRENGT-NOTCH-TOUGHNESS RELATION FOR EXPERIMENTALHY-180/210 WELD METALS
DRAWN~~AE~E UVI ms 0ByANCH,'b
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